# On a General Bayesian Pattern Logic of Frequency-Based Logical Inclusion Fallacies

- Momme von Sydow,
*University of Göttingen*

## Abstract

Bayesian logic provides a rational model of probability judgments
deviating from the standard extensional norm of extensional probability. It
formalizes the general idea of an inductive pattern logic that may resolve
paradoxes of inclusion. Bayesian logic predicts that it should be possible to
generalize the phenomenon of frequency-based logical conjunction fallacies to a
system of logical inclusion fallacies. In Experiment 1 quantitative conditions
for conjunction fallacies and the role of negations are investigated. Experiment
2 provides a first test of the postulated more general system of logical
inclusion fallacies. The results of both experiments confirmed the proposed
pattern logic and its formalization as Bayesian logic. Other theories of the
conjunction fallacy cannot readily explain this class of frequency-based and
pattern-based inclusion fallacies. Whether there are simpler heuristics that may
perhaps explain these data as well should be investigated in the future.

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